The present invention relates to radio communications, and in particular, to high speed data transfers in a radio communications network.
In a cellular communications system, a mobile radio station communicates over an assigned radio channel with one or more base stations. Several base stations are connected to a switching node, which is typically connected to a gateway that interfaces the cellular communications system with other communications systems. A call placed from an external network to a mobile station is directed to the gateway, and from the gateway through one or more nodes to one or more base stations serving the called mobile station. One or more base stations page the called mobile station and establish a radio communications channel. A call originated from the mobile station follows a similar path in the opposite direction except that there is no paging step.
In a Code Division Multiple Access (CDMA) mobile communication system, spreading codes are used to distinguish information associated with different mobile stations or base stations transmitting over the same radio frequency band. In other words, individual radio xe2x80x9cchannelsxe2x80x9d correspond to and are discriminated on the basis of these codes. Various aspects of CDMA are set forth in one or more textbooks such as Applications of CDMA and Wireless/Personal Communications, Garg, Vijay K. et al., Prentice-Hall 1997.
Spread spectrum communications permit mobile transmissions to be received at two or more (xe2x80x9cdiversexe2x80x9d) base stations and processed simultaneously to generate one received signal. With these combined signal processing capabilities, it is possible to perform a handover from one base station to another, (or from one antenna sector to another antenna sector connected to the same base station), without any perceptible disturbance in the voice or data communications. This kind of handover is typically called soft or diversity handover.
Certain problems must be considered in a CDMA communications system. Because all users transmit information using the same frequency band at the same time, each user""s communication interferes with the communications of the other users. Therefore, the power of radio transmitters in a CDMA system must be carefully controlled. Another problem is that the physical characteristics of a radio channel vary significantly. For example, the signal propagation loss between a radio transmitter and receiver vanes as a function of their respective locations, obstacles, weather, etc. As a result, large differences may arise in the strength of signals received at a radio receiver from different radio transmitters. If the transmission power of a radio transmitter signal is too low, the receiver may not correctly decode a weak signal, and the signal will have to be corrected (if possible) or retransmitted. Erroneous receipt of signals adds to congestion in a cell.
Accordingly, desired transmit powers are allocated to down link traffic channels, (i.e., downlink is in the base-to-mobile direction), so that the mobile stations receive the traffic information at an appropriate signal level. The transmit power allocated to such traffic channels may be adjusted to accommodate changing channel conditions resulting from movements of mobile stations, multipath propagation, weather, obstacles, and a current interference level experienced in a cell. But the problem with increasing transmissions of one communication is that it adversely impacts other communications in the same cell or even adjacent cells by increasing the interference level for those other communications. Thus, the transmit power levels corresponding to those other communications may also be increased in response to the increased interference which further compounds the overall interference problem. When the traffic load in a particular cell among the plurality of cells in a mobile communications network exceeds an overload condition, (e.g., the capacity of existing traffic channels, a total traffic channel power level, etc.), that cell is forced to block new mobile radio calls, or to even drop existing calls, in particularly severe overload conditions. In both cases, the system performance is adversely impacted.
As third generation cellular systems have evolved to provide a wide variety of data services as well as speech services involving mobile subscribers, the need for high speed data transfer service has become particularly important. Unfortunately, high speed transfer of large amounts of data competes with limited radio resources, including radio bandwidth, transmit power, and signal/data processing resources (both software and hardware), needed to support such high speed data services. Faced with insufficient bandwidth, transmit power, signal data processing resources, or other resources to support the high speed data transfer, a service request may be rejected or significantly delayed.
The following is a simple example where two users A and B are conducting a speech conversation via their respective mobile terminals, a user A indicates a desire to send a large data file to user B.
User A: xe2x80x9cI have an electronic slide presentation that describes exactly what I am talking about.xe2x80x9d
User B: xe2x80x9cCan I have a look at it?xe2x80x99xe2x80x9d
User A: xe2x80x9cSure, you can see it . . . now.xe2x80x9d
User B: After taking a look at slide says, xe2x80x9cAh, I see your point . . . xe2x80x9d
If the radio bandwidth, transmit power, or signal/data processing resources are insufficient at the time of this conversation to support that electronic slide data file transfer, the file transfer request will either be rejected or the transfer will be delayed for a significant period of time. Both scenarios cause some user irritation, particularly if the delay is for an indeterminate period of time.
Although it is possible to increase the transmit power of user A""s mobile terminal in order to send the large data file, the increased transmit power adversely impacts other connections by adding to the interference experienced by other users. Of course, additional radio bandwidth or signal/data processing resources may be requested and allocated to a user to accommodate high speed transfer of the data file. But those resources may not always be available. Thus, there is a need to provide transfer of a data file at high speed when the available resources are not sufficient to complete the data transfer in a reasonably short period of time. The present invention meets this need without having to increase transmit power.
It is an object of the present invention to accommodate high speed data file or large data packet transfer in a mobile radio communications system.
It is a further object of the present invention to accomplish high speed data file or large data packet transfer without significantly increasing transmit power.
It is a further object of the present invention to accommodate high speed data file or large data packet transfer even when available radio and signal/data processing resources are not sufficient to complete that transfer in a reasonably short period of time.
These objects are accomplished without significantly impacting current services being provided to other users.
In a mobile radio communications system, first radio resources are allocated to a first mobile radio communication. The term xe2x80x9cradio resourcesxe2x80x9d refers to one or more resources used to support a mobile radio communication. Specific examples of radio resources include radio bandwidth, transmit power, signal and data processing hardware and software resources, radio transceiving resources, etc. A second group of radio resources is allocated to a second mobile radio communication. When a block of user information needs to be transmitted that requires an additional amount of radio resources, the first and second mobile radio communications are interrupted or their service levels are reduced for a time period (hopefully brief). At least part of the block of information is transmitted during that time period using at least some of the first and second radio resources allocated for the first and second mobile radio communications. In one example and non-limiting embodiment of the invention, an interruption may be performed using a discontinuous transmission (DTX) operation.
After that time period, transmission of the first and second mobile radio communications is resumed at full (or partial) service levels. The resumed transmission may be a full resumption, where all of the allocated first and second resources are restored to first and second communications. Alternatively, when a part of the data block remains to be transmitted, the resumed transmission may be a partial resumption, with only part of those first and/or second radio resources being restored. The remaining resources are used to transmit the remainder of the block of information (if any). In the partial resumption approach, the first and/or second mobile radio communication may experience a decreased level of communications service. One way in which the partial resumption may be implemented is to alternately interrupt and resume one of the first and second mobile radio communications in cyclic fashion until the block of information is transmitted.
In an example application of the invention, the mobile communications system is a Code Division Multiple Access (CDMA) system, where mobile communication channels are associated with spreading codes. As a result, the radio resources include spreading codes. Other examples of radio resources include increased transmit power, radio signal processing resources, and radio bandwidth resources. In this example embodiment, the invention is applied to downlink communications from a radio network to mobile radios. However, the invention may also be applied to uplink communications from the mobile radios to the radio network.